com.aliyun.odps.io

Class NullWritable

java.lang.Object

com.aliyun.odps.io.NullWritable

All Implemented Interfaces:

Writable, WritableComparable, Comparable

public class NullWritable
extends Object
implements WritableComparable

NullWritable 提供了 null （空值）的 Writable 和 WritableComparable 的实现.

NullWritable 使用单子模式，不允许自行创建，只能通过 get() 方法取得。

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	NullWritable.Comparator NullWritable 对象的 WritableComparator 实现.

Method Summary

Modifier and Type	Method and Description
int	compareTo(Object other) 比较两个 NullWritable 的值.
boolean	equals(Object other) 判断两个对象是否相等.
static NullWritable	get() 获取 NullWritable 实例.
int	hashCode() 返回哈希值 0.
void	readFields(DataInput in) NullWritable 不读入任何内容
String	toString()
void	write(DataOutput out) NullWritable 不输出任何内容

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Detail

get

public static NullWritable get()

获取 NullWritable 实例.

NullWritable 使用单子模式，不允许自行创建，只能通过本方法取得。

Returns:

NullWritable 实例

toString

public String toString()

Overrides:

toString in class Object

hashCode

public int hashCode()

返回哈希值 0.

Overrides:

hashCode in class Object

compareTo

public int compareTo(Object other)

比较两个 NullWritable 的值.

Specified by:

compareTo in interface Comparable

Parameters:

other - 比较对象

Returns:

如果 other 也为 NullWritable，返回0，否则抛 ClassCastException 异常

equals

public boolean equals(Object other)

判断两个对象是否相等.

Overrides:

equals in class Object

Parameters:

other - 比较对象

Returns:

如果 other 也为 NullWritable，返回true，否则，返回false

readFields

public void readFields(DataInput in)
                throws IOException

NullWritable 不读入任何内容

Specified by:

readFields in interface Writable

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

NullWritable 不输出任何内容

Specified by:

write in interface Writable

Throws:

IOException